Former Massachusetts Gov. Mitt Romney and former House Speaker Newt Gingrich talk at the end of the South Carolina Republican presidential candidate debate in Myrtle Beach, S.C., Monday, Jan. 16, 2012.

But attention will be focused on the two front-runners with the most to win – or lose – in a campaign that has become increasingly divisive as it accelerates through major states toward Super Tuesday and beyond.

For Mr. Romney, it’s the impression that he belongs to what Occupy Wall Streeters call the “1 percent” – wealthy beyond the dreams of most Americans and clueless about what those Americans' lives are like.

He’s acknowledged that his tax rate likely is a relatively low 15 percent, some of his investments are parked in a Cayman Islands tax haven, and he seems to think that earning nearly $400,000 a year just in speaking fees is “not very much.” Under pressure from supporters like New Jersey Gov. Chris Christie (not to mention Democrats), Romney now seems likely to make public his tax returns.

For Gingrich, it’s renewed questions of character – specifically, assertions by his second wife in interviews (one of which is to be aired just after Thursday night's debate) that the former speaker asked for an “open marriage” in order to continue an affair with the congressional staffer who later became his third wife.

Even though it might be a “he said, she said” story, any reminder of Gingrich’s acknowledged infidelities and multiple marriages can’t be helpful in a state and party where evangelical Christians are prominent and most likely primary voters describe themselves as socially conservative.

Gingrich backers hope that contrition and redemption dominate that story line.

"Newt is not perfect but who among us is?" Perry said at his withdrawal announcement Thursday morning. "There is forgiveness for those who seek God."

Meanwhile, establishment Republicans are firing back at Gingrich’s blasts at Romney.

His criticisms of the former governor regarding his years in the private sector reorganizing businesses are “dangerous,” amounting to “talking points straight out of Barack Obama's campaign playbook,” warns Sen. John McCain, who headed the Republican ticket in 2008 and who recently endorsed Romney.

Former New Hampshire governor and White House chief of staff John H. Sununu warns of an “October surprise” if Gingrich is nominated and then faces new revelations about the ethics committee probe that led to the end of his House speakership.

At first glance, Gingrich would seem to have the momentum in his fierce relationship with Romney.

Romney’s 18-point lead over Gingrich in South Carolina from earlier this month has dropped to 10 percent, according to a new CNN/Time/Opinion Research poll – down four points for Romney, up five points for Gingrich.

“Gingrich’s standing-O debate performance on Monday night in Myrtle Beach, hailed by national and state activists as a pitch-perfect defense of conservatism, may have moved the needle even further,” writes Adam Sorensen at Time’s “Swampland” political site. “A flash poll taken Tuesday night by Rasmussen found Gingrich pulling within three points of Romney.”

“Among Republican primary voters nationwide, 34 percent think Romney is the GOP candidate who would do a better job managing the economy, but almost as many (29 percent) feel Gingrich would do the better job,” Rasmussen reported Wednesday. “When it comes to national security and defense, Gingrich is the clear leader: 43 percent think he would do a better job versus 18 percent who say the same of Romney.”

The Real Clear Politics average of most recent polls has Romney ahead by just 1.2 percentage points in South Carolina. Two other polls – American Research Group and InsiderAdvantage – put Gingrich ahead by a nose.

Political scientists Lynn Vavreck, of UCLA, and John Sides, of George Washington University, note that Romney’s position among the Republican electorate – generally, a less-than-overwhelming 25 percent or so – actually is good within a crowded field of what until very recently had been seven candidates.

More Republicans pick Romney as their second choice than any other candidate. And when voters are asked to choose between just two GOP candidates – Romney and Gingrich – a solid majority (66 to 34 percent) pick Romney, according to the YouGov research organization that professors Vavreck and Sides write for.

It’s always possible that one of the remaining candidates could have an “Oops!” moment in Thursday night’s debate. Rick Perry’s was probably the beginning of the end for him.

Absent that, the contest between Romney and Gingrich is likely to remain very, very close when South Carolinians go to the polls this Saturday.

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Watch this video on key issues on the minds of social conservative or values voters in South Carolina.